In a radio communications system, downlink transmission refers to a process in which a base station sends a signal to a user equipment. A downlink signal generally includes a data signal and a control signal. HSDPA (High Speed Downlink Packet Access) is a packet-based data service and may enhance a data transmission rate during downlink transmission. An HSDPA technology may be applied in a WCDMA (Wideband Code Division Multiple Access) system. In the WCDMA system, a base station is generally called a Node B (Base station) and a user equipment or a mobile terminal is generally called a UE (user equipment). Generally, an area covered by one NodeB is split into three or six sectors and each sector provides at least one cell.
To implement a function and a feature of HSDPA, HSDPA introduces three new channels in a physical layer specification: an HS-PDSCH (High-Speed Downlink Packet Access), an HS-SCCH (High-Speed Shared Control Channel), and an HS-DPCCH (Uplink High-Speed Dedicated Physical Control Channel). Simply speaking, on the one hand, a cell uses an HS-PDSCH channel to send a data signal in a downlink signal to a UE and uses an HS-SCCH channel to send a control signal in the downlink signal to the UE, where the control signal may be used to demodulate and decode the data signal and for other purposes; on the other hand, after receiving the data signal, the UE performs, according to the control signal, processing such as demodulation and decoding of a corresponding data signal and then uses an HS-DPCCH channel to feed back HARQ-ACK information (Hybrid Automatic Repeat Request-ACK) indicating a reception state to the cell, where the HARQ-ACK information may be ACK/NACK/DTX information, where, ACK indicates that the UE correctly receives the data signal, NACK indicates that the UE does not correctly receive the data signal, and DTX indicates that the UE does not detect data or that the cell is in an inactive state. One of key technologies used in this process, that is, HSDPA, is HARQ (Hybrid Automatic Repeat Request).
However, to further improve the data transmission rate during downlink transmission, it is further hoped that a multi-carrier/multi-cell technology and a multiflow transmission technology are introduced in the prior art. The multi-carrier/multi-cell technology introduces concepts of a serving cell and an assisting serving cell to enable one UE to simultaneously adopt two HSDPA provided by two or more cells (two cells are used as an example in this document) to collaboratively transmit downlink signals, which further improves the data transmission rate during downlink transmission. Meanwhile, the UE may use one HS-DPCCH channel provided by the serving cell to jointly feed back HARQ-ACK information to the serving cell and the assisting serving cell within one timeslot at the same time. The multiflow transmission technology may be considered as an extension of the multi-carrier/multi-cell technology. A greatest difference is that the multi-carrier/multi-cell technology requires the serving cell and the assisting serving cell to have same coverage and a same downlink channel timing relationship while the multiflow transmission technology does not require the serving cell and the assisting serving cell to have the same downlink channel timing relationship. The multiflow transmission technology is also called Multiflow Transmission, MF-Tx for short.
In a process of implementing the present invention, the inventors find that the prior art has at least the following problems: Because the multiflow transmission technology does not require the serving cell and the assisting serving cell to have the same downlink channel timing relationship whereas the UE needs to use a same HS-DPCCH to jointly encode two pieces of HARQ-ACK information of the serving cell and the assisting serving cell in a same timeslot to perform feedback, if it is hoped that the multiflow transmission technology is adopted, a timing problem will occur when the serving cell and the assisting serving cell have different downlink channel timings, for example, a case that the UE cannot determine how to feed back a corresponding message reception state occurs.